Removal of acetylene from gases



Patented July 3, 1945 2,379,610 4 REMOVAL or- A'CETYLENE mom GASES Charles E. Welling and Harold J. Hepp, Bartlesville, kla., assignors to Phillips ,Petroleum Company, a corporation of Delaware No Drawing.

Application January 24, 1942, Serial No. 428,120

3 Claims. (or. 260-677) This invention relates to the removal of acetylene from gases.

When mixtures of hydrocarbons are processed by thermal or catalytic treatment to produce more valuable materials or 'are treated in some other fashion, it often happens that the presence of even minute quantities of acetylene will give rise to objectionable side reactions or to deposition of pressure. A preferred pressure. range would be about 400 to 1000 lbs. per sq. in. gauge.

Suitable temperatures for operating our proc- I ess are in the range 100 to 450 0., and the exact carbon. In consequence it is sometimes desirable to treat such mixtures in such a fashion as to remove the acetylene without destroying valuable components of the mixtures;

It is already known that acetylene may be removed from gases containing it by passing the gases over bauxite or over the usual hydrogenation catalysts such as reduced nickel. With gases containing hydrogen and certain unsaturated hydrocarbons, undesirable reactions may occur over these catalysts in addition to the conversion of acetylene. Furthermore, such catalysts may present special problems in manufacture and handling due to lack of mechanical strength, need for supporting the active catalytic material on an inert carrier, difficulty in preparing a catalyst of'uniform composition and activity, and the like.

We have now found that by leading hydrocar bon gases containing acetylene and hydrogen at elevated temperatures in the range 100 to 400 C. over catalysts comprising alloys whose major constituents are iron, chromium and nickel the acetylene maybe very greatly reduced in amount or practically quantitatively removed without materially altering other hydrocarbon components.

Said alloys may or may not-contain minor amounts of such substances as carbon, silicon,

' phosphorus and the like and may or maynot contain small amounts of substances of thetype of stabilizing agents for steels such as titanium, columbium, molybdenum and the like.

.Since the catalysts are metallic in nature, they may be utilized in a large number of mechanical shapes and forms. Thus the catalysts may be in the form of turnings, borings, chips and the like temperature to be used in a particular application of our process will be determined by such factors as flow velocity of the gas over the catalyst and composition of the gas being treated, permissible acetylene content of the treated gas, 'pre-' vious use of the catalyst and the like.

The alloy catalysts according to our invention are relatively immune to sulfur poisoning and in,

fact minute quantities of sulfur, of the order of'a' few thousandths of one per cent in the gases to be treated, may render the catalyst more selective in its action upon the acetylene present and hence such amounts of sulfur may be desirable in the form of hydrogen sulfide, mercaptans or the like. The presence of appreciable amounts of sulfur in the gases to be treated may require some increase in the temperature of the catalyst within the range already specified.

After a period of use the alloy catalysts accordto our invention may lose activity and can be regenerated by burning out in an oxygen-bearing gas stream. After burning the carbonaceous residues, it may bedesirable to treat the catalysts on may be used in such forms as wire, sheets, or

plates, pipes and tubes and the like.

The alloys used as catalysts in our process may be composed of chromium in weight per cezit ranging from about 5 to about 30, nickel from zero to about 20 weight per cent, and iron as the third major ingredient. A preferred catalyst composition is one containing chromium, nickel and iron in about the weight ratio of 18 8:74.

We may carry out our process at any suitable with a gas containing hydrogen at temperatures in the range 100-600 C.; however, such treatment may sometimes be omitted when the gas to be subsequently treated to remove acetylene contains substantial amounts of hydrogen.

The following examples represent certain specific embodiments of our process. Example 1, in

which no catalyst was used, is cited-merely to show'that very little acetylene can be reacted.

without a catalyst under the conditions of temperature and pressure that are comprehended in our catalytic process. The examples'ai'e not to be construed as unnecessarily limiting the .invention. 7 I

Example 1 A synthetic gas inixture containing about 24 per cent hydrogen, '74 per cent ethylene plus propylene, 0.8% acetylene and small amounts of paramns was passed through a heated quartz tube. Attube temperatures 011300 to.325 0., apressure of 735 to 745 lbs. persq. in. and a space velocity of 90 to 260, from to 91 per cent or the Example 2 Fifteen cubic centimeters of small turnings or a commercial 16 per cent chrome iron were used acetylene survived and was found in the eflluent gas. f r

as catalyst and were contained in a catalyst tube of the same material. The catalyst had been used in previous tests and had twice been reactivated by burning out with air. A synthetic gas mixture containing about 24 per cent hydrogen, 74.5 per cent ethylene plus proplyene, 0.98 per cent acetylene, 0.013 per cent hydrogen sulphide, and small amounts of parafllnic constituents was passed at 720 to 750 lbs. per sq. in. gauge pressure over the catalyst at a rate of45.3 liters per hour (measured at atmospheric temperature and pressure). With the catalyst maintained at a temperature between 340 and 350 C., a sample of effluent gas was taken-during the fourteenth hour of operation and the acetylene content was found to have been reduced to 0.06 per cent acetylene. There was no concurrent destruction of olefins.

Example 3 Fifteen cubic centimeters of small turnings of a commercial 25 per cent chrome, 12 per cent nickel steel were used as a catalyst and were contained in a catalyst tube of the same material.

The catalyst had been used in previous tests and had twice been reactivated by burning out with air at 450 to 500 C. A synthetic gas mixture containing about 24 per cent hydrogen, 73.6 per cent ethylene plus propylene, 0.68 per cent acety- Example 4 Fifteen cubic centimeters of small turnings of a commercial 18 per cent chrome, 8 per cent nickel steel were used as a catalyst and were contained in a catalyst tube of the same material. The catalyst had been burned off with air at temperatures up to 600? C. before use. A synthetic gas mixture containing about 23 per cent hydrogen, 75.4 per cent propylene plus ethylene, 0.51 per cent acetylene, 0.006 per cent hydrogen sulfide and small amounts of parafiinic constitue'nts was passed at a pressure of 750 lbs. per sq. in. gauge over the catalyst at a rate of about 45 liters per hour of gas measured at atmospheric pressure and temperature. With the catalyst maintained at a temperature of 290 C. a sample of efliuent gas was taken during the eleventh hour of operation and the acetylene content was found to have been reduced to less than 0.01 per cent acetylene. No concurrent hydrogenation of olefins was detectable.

- Example Using the same catalyst, charge. stock and flow rate that were described in Example 4, at a catalyst temperature of 275 C. and 400 lbs. per sq. in. gauge pressure, the acetylene content in the efiiuent gas was found to have been reduced to 0.01 per cent acetylene. No concurrent hydrogenation of olefins was detectable.

Example 6 an intervening burning all with air and reduction with hydrogen. The acetylene-bearing gas mixture was passed over the catalyst at a temperature of 160. C. and flow rate of 40.5 liters per hour of gas measured at atmospheric pressure and temperature. A sample of eflluent gas contained less than 0.05 per cent acetylene. No concurrent hydrogenation of olefins was detectable.

Our invention applies particularly to the removal of acetylenes from gases formed by the high-temperature, low-pressure pyrolyses of lowboiling hydrocarbons. In such cases the gases contain suflicient hydrogen for treatment in accordance with our invention, but in the treatment of gases qfsimilar. composition but deficient in hydrogen, hydrogen from an outside source may, of course, be added in such amounts as may be'found necessary for any particular case. Our invention particularly applies to olefin-containing gases where the olefin content exceeds the acetylene content, particularly to gases containing 5% or less of acetylenes, and will find particular use in the treatment of gases containing no more than 1% of acetylenes.

We claim:

1. A process for treating av normally gaseous mixture containing olefins, free hydrogen and a minor amount of acetylene to hydrogenate said acetylene without appreciable hydrogenation of said olefins, which comprises passing said mixture at a temperature between 100 and 400 C. under a superatmospheric pressure into contact with a I steel of large suriacecontaining between'lfi and 25 per cent chromium and not more than about 12 per cent nickel for a time sufilcient to efiect substantially complete removal of said acetylene, said olefins remaining substantially unreacted. 2. The process of claim 1 in which said gaseous mixture contains not more than 1% of acetylene.

3. A process for the selective removal of acetylene from a normally gaseous mixture containing substantial amounts of free hydrogen and olefins and acetylene in an amount less than that of said olefins and not greater than about 5 percent of said mixture, without appreciable decrease in the olefin content, which comprises contacting said mixture at a temperature between about 100 and about 400 C. and a. pressure between about 400 and about 1000 pounds per square inch with a catalytic agent consisting of an alloy of chromium, nickel and iron in a. weight ratio of about 18:8:74 and in a physical form having alarge surface for a time suflicient to effect substantially complete conversion of acetylene and such as to effect substantially no conversion of said olefins.

CHARLES E. WELLING. HAROLD J. HEPP. 

